Compositions and methods for dry electrode films including microparticulate non-fibrillizable binders

ABSTRACT

Provided herein are dry process electrode films, and energy storage devices incorporating the same, including a microparticulate non-fibrillizable binder having certain particle sizes. The electrode films exhibit improved mechanical and processing characteristics. Also provided are methods for processing such microparticulate non-fibrillizable electrode film binders, and for incorporating the microparticulate non-fibrillizable binders in electrode films.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated by reference in their entirety under37 CFR 1.57. This application claims the benefit of U.S. patentapplication Ser. No. 16/366,220, filed Mar. 27, 2019, which claims thebenefit of U.S. Provisional Patent Application No. 62/650,903, filedMar. 30, 2018, entitled “COMPOSITIONS AND METHODS FOR DRY ELECTRODEFILMS INCLUDING MICROPARTICULATE NON-FIBRILLIZABLE BINDERS”, theentirety of each of which are hereby incorporated by reference for allpurposes.

BACKGROUND Field

The present invention relates generally to energy storage devices, andspecifically to materials and methods for dry electrode films includingmicroparticulate non-fibrillizable binders.

Description of the Related Art

Electrical energy storage cells are widely used to provide power toelectronic, electromechanical, electrochemical, and other usefuldevices. Such cells include batteries such as primary chemical cells andsecondary (rechargeable) cells, fuel cells, and various species ofcapacitors, including ultracapacitors. Increasing the operating powerand energy of energy storage devices, including capacitors andbatteries, would be desirable for enhancing energy storage, increasingpower capability, and broadening real-world use cases.

Energy storage devices including electrode films combining complimentaryattributes may increase energy storage device performance in real-worldapplications. Furthermore, existing dry and solvent-free methods offabrication may impose a practical limit to the composition of anelectrode. Thus, new electrode film formulations, and methods for theirfabrication, may result in expanded possibilities for electrode filmformulation, and consequently in improved performance.

SUMMARY

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention aredescribed herein. Not all such objects or advantages may be achieved inany particular embodiment of the invention. Thus, for example, thoseskilled in the art will recognize that the invention may be embodied orcarried out in a manner that achieves or optimizes one advantage orgroup of advantages as taught herein without necessarily achieving otherobjects or advantages as may be taught or suggested herein.

In a first aspect, a self-supporting dry electrode film including amicroparticulate, non-fibrillizable binder having particle sizes ofabout 0.5 μm to about 40 μm is provided.

In a second aspect, a dry electrode film of an energy storage device isprovided. The dry electrode film includes a dry active material and adry binder comprising a fibrillizable binder and a microparticulatenon-fibrillizable binder having a D₅₀ particle size of about 0.5-40 μm,and wherein the dry electrode film is free-standing.

In some embodiments, the microparticulate non-fibrillizable binder has aD₅₀ particle size of about 1-25 μm. In some embodiments, the dry bindercomprises up to 50 wt. % of the microparticulate non-fibrillizablebinder.

In some embodiments, the microparticulate non-fibrillizable binder isselected from at least one of cellulose and a cellulose derivative. Insome embodiments, the microparticulate non-fibrillizable binder isselected from at least one of cellulose, a cellulose ester, a celluloseether, cellulose nitrate, a carboxyalkylcellulose, a cellulose salt anda cellulose salt derivative. In some embodiments, the microparticulatenon-fibrillizable binder is selected from at least one of cellulose,cellulose acetate, methylcellulose, ethylcellulose,hydroxylpropylcellulose (HPC), hydroxyethylcellulose (HEC), cellulosenitrate, carboxymethylcellulose (CMC), carboxyethylcellulose,carboxypropylcellulose, carboxyisopropylcellulose, sodium cellulose,sodium cellulose nitrate and sodium carboxyalkylcellulose. In someembodiments, the microparticulate non-fibrillizable binder is selectedfrom at least one of carboxymethylcellulose (CMC) and polyvinylidenefluoride (PVDF). In some embodiments, the cellulose or the cellulosederivative has a number average molecular weight of about 10,000 toabout 500,000. In some embodiments, the cellulose derivative has adegree of substitution of about 0.7 to about 1.5.

In some embodiments, the fibrillizable binder comprisespolytetrafluoroethylene (PTFE). In some embodiments, the dry electrodefilm is substantially free of holes, cracks and surface pits. In someembodiments, the dry electrode film has a tensile strength of at leastabout 1 N. In some embodiments, the dry active material comprisesgraphite.

In a third aspect, an electrode comprising the dry electrode film incontact with a current collector is provided. In a fourth aspect, alithium ion battery comprising the electrode is provided.

In a fifth aspect, a method of fabricating a dry electrode film of anenergy storage device is provided. The method includes processing a drynon-fibrillizable binder at high shear to form a dry microparticulatenon-fibrillizable binder, combining a dry fibrillizable binder with thedry microparticulate non-fibrillizable binder to form a dry electrodefilm mixture, and calendering the dry electrode film mixture to form afree-standing dry electrode film.

In a sixth aspect, a method of fabricating a dry electrode film of anenergy storage device is provided. The method includes providing a drymicroparticulate non-fibrillizable binder, mixing the drymicroparticulate non-fibrillizable binder with a dry first activematerial by a first nondestructive mixing process to form a dry bulkactive material mixture, mixing a dry fibrillizable binder with a seconddry active material by a high shear mixing process to form a drystructural binder mixture, mixing the dry bulk active material mixtureand the dry structural binder mixture by a second nondestructive mixingprocess to form a dry electrode film mixture, and producing a freestanding dry electrode film from the dry electrode film mixture.

In some embodiments, the method further comprises processing a drynon-fibrillizable binder at high shear to form the dry microparticulatenon-fibrillizable binder.

All of these embodiments are intended to be within the scope of theinvention herein disclosed. These and other embodiments of the presentinvention will become readily apparent to those skilled in the art fromthe following detailed description of the preferred embodiments havingreference to the attached figures, the invention not being limited toany particular preferred embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

FIG. 1 depicts an embodiment of an energy storage device.

FIG. 2A is a photograph of the inside of a grind chamber of a jet millwith three jets pointing at the same point. FIG. 2B is an image of aclassifier with a spinning wheel that selects an output size ofparticles.

FIG. 3A depicts an SEM image of commercially available CMC particles.FIG. 3B depicts jet-milled CMC particles that have been treatedaccording to Example 1.

FIG. 4 provides a chart providing charge and discharge specificcapacities for dry graphite anodes fabricated according to Example 1,and compare anodes fabricated with commercially available CMC and milledCMC.

FIG. 5A depicts an image of an anode film prepared with commerciallyavailable CMC particles. FIG. 5B depicts an image of an anode filmprepared with jet milled CMC particles according to the treatment ofExample 1.

FIG. 6 provides a flow chart depicting a method for fabricating afree-standing electrode film by combining non-fibrillizable binder withfibrillizable binder.

FIG. 7 provides a flow chart depicting a method for parallel processingof electrode film binders.

DETAILED DESCRIPTION

Provided herein are various embodiments of electrode films for use inenergy storage devices. In particular, in certain embodiments, energystorage devices disclosed herein include electrode films including amicroparticulate non-fibrillizable binder having certain particle sizes.The electrode films were discovered to exhibit improved mechanical andprocessing characteristics. Also provided are methods for processingsuch microparticulate non-fibrillizable electrode film binders, and forincorporating the microparticulate non-fibrillizable binders intoelectrode films. The present disclosure reveals that increaseduniformity of distribution of materials in electrode films can berealized when the particle sizes of certain components are within theranges provided herein.

Lithium ion batteries have been relied on as a power source in numerouscommercial and industrial uses, for example, in consumer devices,productivity devices, and in battery-powered vehicles. However, demandsplaced on energy storage devices are continuously—and rapidly—growing.For example, the automotive industry is developing vehicles that rely oncompact and efficient energy storage, such as plug-in hybrid vehiclesand pure electric vehicles.

Some components that affect the storage potential of an energy storagedevice include the electrodes, and more specifically, the electrodefilms comprising each electrode in the device. The electrochemicalcapabilities of electrodes, for example, the capacity and efficiency ofbattery electrodes, is governed by various factors. For example,distribution of active material, binder and additive(s); the physicalproperties of materials therein, such as particle size and surface areaof active material; the surface properties of the active materials; andthe physical characteristics of the electrode film, such ascohesiveness, and adhesiveness to a conductive element. Dry processingmethods traditionally used a high shear and/or high-pressure processingstep to break up and commingle electrode film materials, which maycontribute to structural advantages over electrode films produced usinga wet process.

In principle, electrode films having a more uniform distribution ofactive materials, binders, and other components will exhibit higherperformance. Generally, it is thought that electrode films may sufferreduced performance due to the mechanical properties of the filmcomponents, and interactions therebetween. For example, it is thoughtthat mechanical limitations may result from poor adhesion between anactive layer and a current collector, and poor cohesion in the electrodefilm, for example, between active materials and binders. Such processesmay lead to losses in performance in both power delivery and energystorage capacity. It is thought that losses in performance may be due todeactivation of active materials, for example, due to losses in ionicconductivity, in electrical conductivity, or a combination thereof. Forexample, as adhesion between active layers and current collectorsdecreases, cell resistance may increase. Decreases in cohesion betweenactive materials may also lead to increases in cell resistance, and insome cases electrical contact may be lost, removing some active materialfrom the ionic and electrical transfer cycles in the cell. Withoutwishing to be limited by theory, it is thought that volumetric changesin the active materials may contribute to such processes. For example,additional degradation may be observed in electrodes incorporatingcertain active materials, such as silicon-based materials, that undergosignificant volumetric changes during cell cycling. Lithiumintercalation-deintercalation processes may correspond to suchvolumetric changes in some systems. Generally, these mechanicaldegradation processes may be observed in any electrode, for example acathode, an anode, a positive electrode, a negative electrode, a batteryelectrode, a capacitor electrode, a hybrid electrode, or other energystorage device electrode. It is anticipated that increasing uniformityof electrode film materials will mitigate at least some of theseproblems.

More specifically, uniform distribution of binders in an electrode filmmay provide a film with improved mechanical characteristics. Such animprovement may provide a number of practical benefits. For example, anelectrode film having a uniform distribution of binder components mayexhibit reduced incidence of defects and/or reduced severity of defects,compared to an electrode film having poorer distribution of bindermaterials. For further example, an electrode film having a uniformdistribution of binder components may exhibit higher tensile strengthand/or ductility, which may facilitate the manufacture of an energystorage device. Specifically, electrode films having higher tensilestrength and/or ductility may be easier to apply to a current collectoror other substrate. These factors can be especially relevant when dryelectrode processing techniques are used, as the electrode film may behandled as a free-standing film, defined further herein as a“self-supporting film.”

Smaller particle sizes may in principle allow for more uniformdistribution of electrode film materials including active materials,binders, and other components. However, in practice, some components mayaggregate when reduced below a certain size threshold. Thus, theparticle sizes of various components of the electrode film may beadvantageously incorporated within ranges. In the present disclosure, itwas discovered that microparticulate non-fibrillizable binders may beincorporated in electrode films at certain particle sizes. Smallerparticle sizes and more intimate contact of active materials, binders,and additives may be realized, leading to a better device. Smallerparticle sizes may permit the more consistent manufacture of electrodefilms. These electrode films may be made with a reduced variation inproperties between electrode films manufactured using substantiallyidentical processes, and/or under substantially identical conditions.

When an electrode film is produced by a dry, solvent-free process, waterdispersion is not available, and uniform dispersion of the cellulose maybe more difficult to achieve. Commercially available CMC in powder formis generally limited to D₅₀ particle size of approximately 40-70 μm.More specific sizes within this range are limited to certain degrees ofsubstitution. It is thought that the larger particle size fractionpresents various problems such as dispersion inhomogeneity of CMC,localized pressure during calender rolling, adhesion of CMC particles toheated calender rollers, which may lead to problems described hereinsuch as electrode film defects. It is thought that reduction ofcellulose particle size to be commensurate with active materialparticles may ameliorate the problems described herein. As the CMC isbetter dispersed and on the order of the particle size of activematerial particles, calendar pressure is thought to be more uniformlydistributed throughout the electrode film, which may lead to moreconsistency and less damage to the active material particles, such asgraphite particles. Additionally, the improvement in consistency on filmformation may enable the production of a uniform continuous roll film.

Some embodiments include electrode films made by a dry process for usein batteries, where the electrode films include a microparticulatenon-fibrillizable binder having a particle size in the range of 0.5 to40 μm, and at least one fibrillizable binder. Embodiments include dryelectrodes and fabrication processes that provide microparticulatenon-fibrillizable binder particles having the sizes in the range ofabout 0.5 to about 40 μm, and electrode film incorporating suchmicroparticulate non-fibrillizable binder particles. Such electrodefilms may have a more uniform distribution of active materials, binders,and other components. Electrode films incorporating suchmicroparticulate non-fibrillizable binder particles may exhibit improvedtensile strength and/or processability. In certain embodiments, themicroparticulate non-fibrillizable binder is a cellulose, for example,carboxymethylcellulose (CMC). The electrode film may be suitable for useas an anode of a lithium ion battery. In certain embodiments, theelectrode film includes graphite.

A dry or self-supporting electrode film incorporating suchmicroparticulate non-fibrillizable binder particles may provide improvedcharacteristics relative to a typical electrode film. For example, a dryor self-supporting electrode film may provide one or more of improvedfilm strength, improved cohesiveness, improved adhesiveness, improvedelectrical performance, or reduced incidence of defects. The defects mayinclude holes, cracks, surface pits in the electrode film. Theadhesiveness may be adhesiveness to a current collector. The electricalperformance may be specific capacity. The film strength may be tensilestrength.

An electrode film described herein, or an energy storage deviceincorporating an electrode film described herein, may advantageously becharacterized by improved specific capacity (which may be measured inmAh/g). Further improvements that may be realized in various embodimentsinclude reduced capacity fade over the life of the device.

Some embodiments relate to dry electrode processing techniques. Dryelectrode fabrication processes may be as disclosed in one or more ofU.S. Publication No. 2006/0114643, U.S. Publication No. 2006/0133013,U.S. Pat. No. 9,525,168, or U.S. Pat. No. 7,935,155, each of which isincorporated by reference herein in the entirety.

Further provided herein are methods for reducing the particles sizes ofmicroparticulate non-fibrillizable binders. A pressurized jet millingprocess was found to reduce the particle size of the microparticulatenon-fibrillizable binder. For example, a non-fibrillizable binder can beplaced into a jet mill and “jet milled” to reduce the particle size tobe on the order of the median (D₅₀) particle size of the activematerial(s) to be included in the electrode film. In some embodiments,the active material may be graphite having a median particle size ofabout 15 μm. In further embodiments, the microparticulatenon-fibrillizable binder can be a cellulose, for example, CMC. Suitablepressurized jet milling conditions include a grind gas pressure of100-500 psi. The jet milling may include separation of milled particlesby particle size. For example, particles of the microparticulatenon-fibrillizable binder having a given size can be separated by aclassifier.

One embodiment is a method of fabricating a free-standing electrodefilm. With reference to FIG. 6 , the method 600 may include selecting anon-fibrillizable binder (605); jet-milling the non-fibrillizable binderto form a microparticulate non-fibrillizable binder having a medianparticle size (610). Step 610 may comprise milling the non-fibrillizablebinder to result in particles on the order of the active materialparticle size, which may be, for example, about 0.5 to about 40 μm;combining the microparticulate non-fibrillizable binder particles with afibrillizable binder and one or more active materials to form anelectrode film mixture (615); and calendering the electrode film mixtureto form a self-supporting and/or free-standing electrode film (620). Insome embodiments, each step is dry and solvent-free. In someembodiments, the microparticulate non-fibrillizable binder ispolyvinylidene fluoride (PVDF) and/or CMC. In further embodiments, themicroparticulate non-fibrillizable binder is CMC. In still furtherembodiments, the fibrillizable binder is PTFE. In yet furtherembodiments, the active material comprises graphite. A method offabricating a free-standing electrode film may comprise one or moreparallel processing steps as provided in FIG. 7 .

With reference to FIG. 7 , the parallel processing method begins with anupper (as shown) parallel processing path 702 and a lower (as shown)parallel processing path 710. In the upper (as shown) parallelprocessing path 702, a bulk active material mixture 708 is formed bynondestructively mixing a bulk active material 704 with anon-fibrillizable binder 706. The non-fibrillizable binder 706 may be amicroparticulate non-fibrillizable binder, as described previouslyherein. The non-fibrillizable binder 704 may be, for example, PVDFand/or CMC. The bulk active material 706 may be graphite. In the lower(as shown) parallel processing path 710, a second active material 712and a structural binder 714 are combined under nondestructive mixing.The structural binder 714 may be PTFE, and the second active material712 may be graphite. The mixed structural binder and second activematerial form an initial binder mixture 716 that is then jet-milled in ahigh shear, high intensity process to form a structural binder mixture718. The bulk active material mixture 708 is then combined with thestructural binder mixture 718 in a nondestructive mixing process to forma bulk active material and binder mixture 720, which is then processedby a low shear jet milling to form an electrode film mixture 722. Thelow shear jet milling may be performed at a high feed rate, for example,relative to the initial jet milling used to form the structural bindermixture 718. The electrode film mixture 722 may then be pressed orcalendered into a self-supporting and free-standing electrode film 724.Generally, no solvents are required in any stage of the process.

In various embodiments, a dry powder, for example, a mixture includingbinder particles and active material particles, can be mixed by a mildprocess using, for example a convection, pneumatic or diffusion mixer asfollows: a tumbler with and without mixing media (for example, glassbead, ceramic ball), a paddle mixer, a blade blender or an acousticmixer. The mild mixing process may be nondestructive with respect to anyactive materials in the mixture. Without limitation, graphite particlesmay be preserved of size following the mild mixing process. In furtherembodiments, the powder mixing sequence and conditions can be varied toimprove uniform distribution of active material, binder, and optionaladditive(s).

The materials and methods provided herein can be implemented in variousenergy storage devices. As provided herein, an energy storage device canbe a capacitor, a lithium ion capacitor (LIC), an ultracapacitor, abattery, a lithium ion battery, or a hybrid energy storage devicecombining aspects of two or more of the foregoing. In preferableembodiments, the device is a lithium ion battery.

An energy storage device can be of any suitable configuration, forexample planar, spirally wound, button shaped, or pouch. An energystorage device can be a component of a system, for example, a powergeneration system, an uninterruptible power source systems (UPS), aphoto voltaic power generation system, an energy recovery system for usein, for example, industrial machinery and/or transportation. An energystorage device may be used to power various electronic device and/ormotor vehicles, including hybrid electric vehicles (HEV), plug-in hybridelectric vehicles (PHEV), and/or electric vehicles (EV).

FIG. 1 shows a side cross-sectional schematic view of an example of anenergy storage device 100 having an electrode film including amicroparticulate non-fibrillizable binder as provided herein. The energystorage device 100 may be classified as, for example, a capacitor, abattery, a capacitor-battery hybrid, or a fuel cell. In one embodiment,device 100 is a lithium ion battery.

The device has a first electrode 102, a second electrode 104, and aseparator 106 positioned between the first electrode 102 and secondelectrode 104. The first electrode 102 and the second electrode 104 areadjacent to respective opposing surfaces of the separator 106. Theenergy storage device 100 includes an electrolyte 118 to facilitateionic communication between the electrodes 102, 104 of the energystorage device 100. For example, the electrolyte 118 may be in contactwith the first electrode 102, the second electrode 104 and the separator106. The electrolyte 118, the first electrode 102, the second electrode104, and the separator 106 are housed within an energy storage devicehousing 120. One or both of the first electrode 102 and the secondelectrode 104 may comprise a microparticulate non-fibrillizable binderas described herein.

One or more of the first electrode 102, the second electrode 104, andthe separator 106, or constituent thereof, may comprise porous material.The pores within the porous material can provide containment for and/orincreased surface area for contact with an electrolyte 118 within thehousing 120. The energy storage device housing 120 may be sealed aroundthe first electrode 102, the second electrode 104 and the separator 106,and may be physically sealed from the surrounding environment.

In some embodiments, the first electrode 102 can be an anode (a“negative electrode”) and the second electrode 104 can be a cathode (a“positive electrode”). The separator 106 can be configured toelectrically insulate two electrodes adjacent to opposing sides of theseparator 106, such as the first electrode 102 and the second electrode104, while permitting ionic communication between the two adjacentelectrodes. The separator 106 can comprise a suitable porous,electrically insulating material. In some embodiments, the separator 106can comprise a polymeric material. For example, the separator 106 cancomprise a cellulosic material (e.g., paper), a polyethylene (PE)material, a polypropylene (PP) material, and/or a polyethylene andpolypropylene material.

Generally, the first electrode 102 and second electrode 104 eachcomprise a current collector and an electrode film. Electrodes 102 and104 comprise electrode films 112 and 114, respectively. Electrode films112 and 114 can have any suitable shape, size and thickness. Forexample, the electrode films can have a thickness of about 30 microns(μm) to about 250 microns, for example, about 50 microns, about 100microns, about 150 microns, about 200 microns, about 250 microns, about300 microns, about 400 microns, about 500 microns, about 750 microns,about 1000 microns, about 2000 microns, or values therebetween. Theelectrode films generally comprise one or more active materials, forexample, anode active materials or cathode active materials as providedherein. The electrode films 112 and/or 114 may be dry and/orself-supporting electrode films as provided herein, and havingadvantageous properties, such as tensile strength, or capacity, asprovided herein. The first electrode film 112 and/or the secondelectrode film 114 may also include a microparticulate non-fibrillizablebinder as described herein, and may also include one or more additionalbinders. The electrode films 112 and/or 114 may be prepared by a processas described herein. The electrode films 112 and/or 114 may be wet orself-supporting dry electrodes as described herein.

As shown in FIG. 1 , the first electrode 102 and the second electrode104 include a first current collector 108 in contact with firstelectrode film 112, and a second current collector 110 in contact withthe second electrode film 114, respectively. The first current collector108 and the second current collector 110 facilitate electrical couplingbetween each corresponding electrode film and an external electricalcircuit (not shown). The first current collector 108 and/or the secondcurrent collector 110 comprise one or more electrically conductivematerials, and have can have any suitable shape and size selected tofacilitate transfer of electrical charge between the correspondingelectrode and an external circuit. For example, a current collector caninclude a metallic material, such as a material comprising aluminum,nickel, copper, rhenium, niobium, tantalum, and noble metals such assilver, gold, platinum, palladium, rhodium, osmium, iridium and alloysand combinations of the foregoing. For example, the first currentcollector 108 and/or the second current collector 110 can comprise, forexample, an aluminum foil or a copper foil. The first current collector108 and/or the second current collector 110 can have a rectangular orsubstantially rectangular shape sized to provide transfer of electricalcharge between the corresponding electrode and an external circuit.

In some embodiments, the at least one active material includes a treatedcarbon material, where the treated carbon material includes a reductionin a number of hydrogen-containing functional groups,nitrogen-containing functional groups and/or oxygen-containingfunctional groups, as described in U.S. Patent Publication No.2014/0098464. For example, the treated carbon particles can include areduction in a number of one or more functional groups on one or moresurfaces of the treated carbon, for example about 10% to about 60%reduction in one or more functional groups compared to an untreatedcarbon surface, including about 20% to about 50%. The treated carbon caninclude a reduced number of hydrogen-containing functional groups,nitrogen-containing functional groups, and/or oxygen-containingfunctional groups. In some embodiments, the treated carbon materialcomprises functional groups less than about 1% of which containhydrogen, including less than about 0.5%. In some embodiments, thetreated carbon material comprises functional groups less than about 0.5%of which contains nitrogen, including less than about 0.1%. In someembodiments, the treated carbon material comprises functional groupsless than about 5% of which contains oxygen, including less than about3%. In further embodiments, the treated carbon material comprises about30% fewer hydrogen-containing functional groups than an untreated carbonmaterial.

In some embodiments, energy storage device 100 can be a lithium ionbattery. In some embodiments, the electrode film of a lithium ionbattery electrode can comprise a microparticulate non-fibrillizablebinder as described herein, one or more active materials, and afibrillized binder matrix.

In further embodiments, the energy storage device 100 is charged with asuitable lithium-containing electrolyte. For example, device 100 caninclude a lithium salt, and a solvent, such as a non-aqueous or organicsolvent. Generally, the lithium salt includes an anion that is redoxstable. In some embodiments, the anion can be monovalent. In someembodiments, a lithium salt can be selected from hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium bis(trifluoromethansulfonyl)imide (LiN(SO₂CF₃)₂),lithium trifluoromethansulfonate (LiSO₃CF₃), and combinations thereof.In some embodiments, the electrolyte can include a quaternary ammoniumcation and an anion selected from the group consisting ofhexafluorophosphate, tetrafluoroborate and iodide. In some embodiments,the salt concentration can be about 0.1 mol/L (M) to about 5 M, about0.2 M to about 3 M, or about 0.3 M to about 2 M. In further embodiments,the salt concentration of the electrolyte can be about 0.7 M to about 1M. In certain embodiments, the salt concentration of the electrolyte canbe about 0.2 M, about 0.3 M, about 0.4 M, about 0.5 M, about 0.6 M,about 0.7 M, about 0.8 M. about 0.9 M, about 1 M, about 1.1 M, about 1.2M, or values therebetween.

In some embodiments the energy storage device electrolyte can include aliquid solvent. The solvent need not dissolve every component, and neednot completely dissolve any component, of the electrolyte. In furtherembodiments, the solvent can be an organic solvent. In some embodiments,a solvent can include one or more functional groups selected fromcarbonates, ethers and/or esters. In some embodiments, the solvent cancomprise a carbonate. In further embodiments, the carbonate can beselected from cyclic carbonates such as, for example, ethylene carbonate(EC), propylene carbonate (PC), vinyl ethylene carbonate (VEC), vinylenecarbonate (VC), fluoroethylene carbonate (FEC), and combinationsthereof, or acyclic carbonates such as, for example, dimethyl carbonate(DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), andcombinations thereof. In certain embodiments, the electrolyte cancomprise LiPF₆, and one or more carbonates.

In some embodiments, the lithium ion battery is configured to operate atabout 2.5 to 4.5 V, or 3.0 to 4.2 V. In further embodiments, the lithiumion battery is configured to have a minimum operating voltage of about2.5 V to about 3 V, respectively. In still further embodiments, thelithium ion battery is configured to have a maximum operating voltage ofabout 4.1 V to about 4.4 V, respectively.

Definitions

As used herein, the terms “battery” and “capacitor” are to be giventheir ordinary and customary meanings to a person of ordinary skill inthe art. The terms “battery” and “capacitor” are nonexclusive of eachother. A capacitor or battery can refer to a single electrochemical cellthat may be operated alone, or operated as a component of a multi-cellsystem.

As used herein, the voltage of an energy storage device is the operatingvoltage for a single battery or capacitor cell. Voltage may exceed therated voltage or be below the rated voltage under load, or according tomanufacturing tolerances.

As provided herein, a “self-supporting” electrode film is an electrodefilm that incorporates binder matrix structures sufficient to supportthe film or layer and maintain its shape such that the electrode film orlayer can be free-standing. When incorporated in an energy storagedevice, a self-supporting electrode film or active layer is one thatincorporates such binder matrix structures. Generally, and depending onthe methods employed, such electrode films are strong enough to beemployed in energy storage device fabrication processes without anyoutside supporting elements, such as a current collector or other film.For example, a “self-supporting” electrode film can have sufficientstrength to be rolled, handled, and unrolled within an electrodefabrication process without other supporting elements. A dry electrodefilm described herein, such as a cathode electrode film or an anodeelectrode film, may be self-supporting.

As provided herein, a “solvent-free” electrode film is an electrode filmthat contains no detectable processing solvents, processing solventresidues, or processing solvent impurities. A dry electrode filmdescribed herein, such as a cathode electrode film or an anode electrodefilm, may be solvent-free.

A “wet” electrode, “wet process” electrode, or slurry electrode asprovided herein, is an electrode prepared by at least one step involvinga slurry of active material(s), binder(s), and optionally additive(s). Awet electrode generally will include a detectable amount of processingsolvent residues, and/or processing solvent impurities, even after theelectrode is dried, due to the solvents used during processing.

As used herein, a “nondestructive” process is a process in which anelectrode active material, including the surface of the electrode activematerial, is not substantially modified during the process. Thus, theanalytical characteristics and/or performance in an application, such asincorporation in an energy storage device, of the active material, areidentical or nearly identical to those which have not undergone theprocess. For example, a coating on the active material may beundisturbed or substantially undisturbed during the process. Anon-limiting example of a nondestructive process is “nondestructivelymixing or blending,” or jet milling at a reduced pressure, increasedfeed rate, decreased velocity (e.g., blender speed), and/or change inother process parameter(s) such that the shear imparted upon an activematerial remains below a threshold at which the analyticalcharacteristics and/or performance of the active material would beadversely affected, when implemented into an energy storage device. A“nondestructive” process can be distinguished from a high shear processwhich substantially modifies an electrode active material, such as thesurface of an electrode active material, and substantially affects theanalytical characteristics and/or the performance of the activematerial. For example, high shear blending or jet milling can havedetrimental effects on the surface of an electrode active material. Ahigh shear process may be implemented, at the detriment to the activematerial surface characteristics, to provide other benefits, such asfibrillization of binder material, or otherwise forming a binder/activematerial matrix to assist in forming a self-supporting electrode film.Embodiments herein provide similar benefits, while avoiding thedetrimental effects of excessive use of high shear processes. Ingeneral, the nondestructive processes herein are performed at one ormore of a higher feed rate, lower velocity, and/or lower pressure,resulting in a lower shear process than the more destructive processesthat will otherwise substantially modify an electrode active material,and thus affect performance.

In some embodiments, an electrode film as provided herein includes atleast one active material and at least one binder. The at least oneactive material can be any active material known in the art. The atleast one active material may be a material suitable for use in theanode or cathode of a battery. Anode active materials can be comprisedof, for example, an insertion material (such as carbon, graphite, and/orgraphene), an alloying/dealloying material (such as silicon, siliconoxide, tin, and/or tin oxide), a metal alloy or compound (such as Si—Al,and/or Si—Sn), and/or a conversion material (such as manganese oxide,molybdenum oxide, nickel oxide, and/or copper oxide). The anode activematerials can be used alone or mixed together to form multi-phasematerials (such as Si—C, Sn—C, SiOx-C, SnOx-C, Si—Sn, Si-SiOx, Sn-SnOx,Si-SiOx-C, Sn-SnOx-C, Si—Sn—C, SiOx-SnOx-C, Si-SiOx-Sn, orSn-SiOx-SnOx.). The cathode active material can be, for example, a metaloxide, metal sulfide, or a lithium metal oxide. The lithium metal oxidecan be, for example, a lithium nickel manganese cobalt oxide (NMC), alithium manganese oxide (LMO), a lithium iron phosphate (LFP), a lithiumcobalt oxide (LCO), a lithium titanate (LTO), and/or a lithium nickelcobalt aluminum oxide (NCA). In some embodiments, cathode activematerials can be comprised of, for example, a layered transition metaloxide (such as LiCoO₂ (LCO), Li(NiMnCo)O₂ (NMC) and/orLiNi_(0.8)Co_(0.15)Al_(0.05)O₂ (NCA)), a spinel manganese oxide (such asLiMn₂O₄ (LMO) and/or LiMn_(1.5)Ni_(0.5)O₄ (LMNO)) or an olivine (such asLiFePO₄).

The at least one active material may include one or more carbonmaterials. The carbon materials may be selected from, for example,graphitic material, graphite, graphene-containing materials, hardcarbon, soft carbon, carbon nanotubes, porous carbon, conductive carbon,or a combination thereof. A graphite can be synthetic or naturallyderived. Activated carbon can be derived from a steam process or anacid/etching process. In some embodiments, the graphitic material can bea surface treated material. In some embodiments, the porous carbon cancomprise activated carbon. In some embodiments, the porous carbon cancomprise hierarchically structured carbon. In some embodiments, theporous carbon can include structured carbon nanotubes, structured carbonnanowires and/or structured carbon nanosheets. In some embodiments, theporous carbon can include graphene sheets. In some embodiments, theporous carbon can be a surface treated carbon.

In some embodiments, a cathode electrode film of a lithium ion batteryor hybrid energy storage device can include about 70 weight % to about98 weight % of the at least one active material, including about 70weight % to about 92 weight %, or about 70 weight % to about 96 weight%. In some embodiments, the cathode electrode film can comprise up toabout 10 weight % of the porous carbon material, including up to about 5weight %, or about 1 weight % to about 5 weight %. In some embodiments,the cathode electrode film comprises up to about 5 weight %, includingabout 1 weight % to about 3 weight %, of the conductive additive. Insome embodiments, the cathode electrode film comprises up to about 20weight % of binder, for example, about 1.5 weight % to 10 weight %,about 1.5 weight % to 5 weight %, or about 1.5 weight % to 3 weight %.In some embodiments, the cathode electrode film comprises about 1.5weight % to about 3 weight % binder.

In some embodiments, an anode electrode film may comprise at least oneactive material, a binder, and optionally a conductive additive. In someembodiments, the conductive additive may comprise a conductive carbonadditive, such as carbon black. In some embodiments, the at least oneactive material of the anode may comprise synthetic graphite, naturalgraphite, hard carbon, soft carbon, graphene, mesoporous carbon,silicon, silicon oxides, tin, tin oxides, germanium, lithium titanate,mixtures, or composites of the aforementioned materials. In someembodiments, an anode electrode film can include about 80 weight % toabout 98 weight % of the at least one active material, including about80 weight % to about 98 weight %, or about 94 weight % to about 97weight %. In some embodiments, the anode electrode film comprises up toabout 5 weight %, including about 1 weight % to about 3 weight %, of theconductive additive. In some embodiments, the anode electrode filmcomprises up to about 20 weight % of the binder, including about 1.5weight % to 10 weight %, about 1.5 weight % to 5 weight %, or about 3weight % to 5 weight %. In some embodiments, the anode electrode filmcomprises about 4 weight % binder. In some embodiments, the anode filmmay not include a conductive additive.

Some embodiments include an electrode film, such as of an anode and/or acathode, having one or more binders. The one or more binders include amicroparticulate non-fibrillizable binder having a particle size in therange of 0.5 μm to 40 μm as described herein, and in some embodiments,along with a fibrillizable binder. The microparticulatenon-fibrillizable binder may be cellulose or a derivative of cellulose.A derivative of cellulose can include, for example, cellulose esterssuch as cellulose acetate; cellulose ethers such as methylcellulose,ethylcellulose, hydroxylpropylcellulose (HPC), or hydroxyethylcellulose(HEC); cellulose nitrate; or a carboxyalkylcellulose, for example,carboxymethylcellulose (CMC), carboxyethylcellulose,carboxypropylcellulose, or carboxyisopropylcellulose. In furtherembodiments, the cellulose or cellulose derivative may comprise acellulose salt. In still further embodiments, a cellulose salt cationmay be selected from sodium, ammonium, or lithium. For example, thecellulose or cellulose derivative may comprise a sodium cellulose or asodium cellulose derivative selected from a sodium cellulose ester,sodium cellulose ether, a sodium cellulose nitrate, or a sodiumcarboxyalkylcellulose. In preferable embodiments, the microparticulatenon-fibrillizable binder is CMC. The CMC may comprise sodiumcarboxymethylcellulose.

A cellulose derivative may be characterized by its degree ofsubstitution. For example, the degree of substitution may be about 0.7to about 1.5, or about 1.2. Certain degrees of substitution may bedesirable, when the material is implemented within an electrode film, inorder to provide desirable characteristics. However, commerciallyavailable CMC in powder form was found to be limited to certain particlesizes and degrees of substitution. For example, commercially availableCMC powders having a degree of substitution of 1.2 were found to beavailable only in larger particles sizes. Smaller particle sizes down toabout 40 μm were found to be limited to a degree of substitution of 0.7,which was observed to be an unfavorable degree of substitution. Asmentioned above, smaller CMC powder has not been available, as there hasbeen no recognized need for such material, and certainly not at adesirable degree of substitution.

In some embodiments, the cellulose or cellulose derivative may includecrosslinks. Further, a cellulose or cellulose derivative may becharacterized by its molecular weight, which generally is number averagemolecular weight. In some embodiments, the cellulose or cellulosederivative has a number average molecular weight of about 10,000 toabout 500,000, or about 50,000 to about 400,000.

The one or more binders can include polytetrafluoroethylene (PTFE), apolyolefin, polyalkylenes, polyethers, styrene-butadiene, co-polymers ofpolysiloxanes and polysiloxane, branched polyethers, polyvinylethers,co-polymers thereof, and/or admixtures thereof. The binder can include acellulose. The cellulose can be a carboxyalkylcellulose, for example,carboxymethylcellulose (CMC). In some embodiments, the polyolefin caninclude polyethylene (PE), polypropylene (PP), polyvinylidene fluoride(PVDF), co-polymers thereof, and/or mixtures thereof. For example, thebinder can include polyvinylene chloride, poly(phenylene oxide) (PPO),polyethylene-block-poly(ethylene glycol), poly(ethylene oxide) (PEO),poly(phenylene oxide) (PPO), polyethylene-block-poly(ethylene glycol),polydimethylsiloxane (PDMS), polydimethylsiloxane-coalkylmethylsiloxane,co-polymers thereof, and/or admixtures thereof. In certain embodiments,the fibrillizable binder is PTFE. A dry self-supporting electrode filmmay comprise interpenetrating networks of the aforementioned binders. Insome embodiments, the one or more binders comprise CMC, PVDF, and PTFE.

The binder may include various suitable ratios of the polymericcomponents. The microparticulate non-fibrillizable binder can be up to50 weight % of the binder. For example, the microparticulatenon-fibrillizable binder can be about 0.1 weight % to about 50 weight %,about 0.5 weight % to about 10 weight %, about 0.5 weight % to about 5weight %, about 0.5 to about 2 weight %, or about 0.5 to about 1 weight%. PTFE can be up to about 98 weight % of the binder, for example, fromabout 20 weight % to about 95 weight %, about 20 weight % to about 90weight %, including about 20 weight % to about 80 weight %, about 30weight % to about 70 weight %, about 30 weight % to about 50 weight %,or about 50 weight % to about 90 weight %. In some embodiments, the oneor more binders comprises about 0.1 to about 2 weight % CMC, about 0.1to about 2 weight % PVDF, and about 1 to about 4 weight % PTFE. Incertain embodiments, the one or more binders comprises about 1 weight %CMC, about 1 weight % PVDF, and about 2 weight % PTFE.

In some embodiments, the microparticulate non-fibrillizable binderparticles may have a median particle size of about 0.5 μm to about 40μm, for example, about 1 μm to about 25 μm, about 2 μm to about 20 μm,about 5 μm to about 15 μm, or about 10 μm to about 15 μm. The electrodefilm mixture may additionally include binder particles other than themicroparticulate non-fibrillizable binder particles, for example, PTFEbinder particles, having selected sizes. In some embodiments, the binderparticles may be about 50 nm, about 100 nm, about 150 nm, about 200 nm,about 250 nm, about 300 nm, about 350 nm, about 400 nm, about 450 nm,about 500 nm, about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5μm, about 10 μm, about 50 μm, about 100 μm, or values therebetween.

A dry fabrication process can refer to a process in which no orsubstantially no solvents are used in the formation of an electrodefilm. For example, components of the electrode film, including activematerials and binders, may comprise dry particles. The dry particles forforming the electrode film may be combined to provide a dry particleelectrode film mixture. In some embodiments, the electrode film may beformed from the dry particle electrode film mixture such that weightpercentages of the components of the electrode film and weightpercentages of the components of the dry particles electrode filmmixture are substantially the same. In some embodiments, the electrodefilm formed from the dry particle electrode film mixture using the dryfabrication process may be free from, or substantially free from, anyprocessing additives such as solvents and solvent residues resultingtherefrom. In some embodiments, the resulting electrode films areself-supporting films formed using the dry process from the dry particlemixture. In some embodiments, the resulting electrode films arefree-standing films formed using the dry process from the dry particleelectrode film mixture. A process for forming an active layer orelectrode film can include fibrillizing the fibrillizable bindercomponent(s) such that the film comprises a fibrillized binder matrix.In further embodiments, a free-standing electrode film may be formed inthe absence of a current collector. In still further embodiments, anelectrode film may comprise a fibrillized polymer matrix such that thefilm is self-supporting. It is thought that a matrix, lattice, or web offibrils can be formed to provide mechanical structure to the electrodefilm.

In some embodiments, an energy storage device electrode film, whereinthe electrode film is dry and/or self-supporting film including amicroparticulate non-fibrillizable binder described herein, may providea specific capacity on charge or discharge of about 300 mAh/g, about 325mAh/g, about 350 mAh/g, about 375 mAh/g, about 400 mAh/g, about 425mAh/g, about 450 mAh/g, about 500 mAh/g, or a range of valuestherebetween. In further embodiments, an energy storage device electrodefilm, wherein the electrode film is dry and/or self-supporting filmincluding a microparticulate non-fibrillizable binder described herein,may provide a first cycle efficiency of about 90%, about 91%, about 92%,about 93%, or a range of values therebetween.

An electrode film may have a selected thickness suitable for certainapplications. The thickness of an electrode film as provided herein maybe greater than that of an electrode film prepared by conventionalprocesses. In some embodiments, the electrode film can have a thicknessof about 250 microns, about 300 microns, about 350 microns, about 400microns, about 450 microns, about 500 microns, about 750 microns, about1 mm, or about 2 mm, or a range of values therebetween.

In some embodiments, a free-standing and/or self-supporting electrodefilm including a microparticulate non-fibrillizable binder describedherein may have a tensile strength of at least about 1 N. In furtherembodiments, the tensile strength may be about 1 N, about 1.1 N, about1.2 N, about 1.3 N, about 1.4 N, about 1.5 N, about 1.6 N, about 1.7 N,about 1.8 N, about 1.9 N, about 2 N, greater than about 2 N, or a rangeof values therebetween.

In some embodiments, a set (of, e.g., at least 3 electrode films) offree-standing and/or self-supporting electrode films including amicroparticulate non-fibrillizable binder described herein fabricatedunder substantially identical conditions may have variation in specificcapacity of less than about 3% standard deviation (sd), for example,about 2.5% sd, about 2% sd, about 1.5% sd, about 1% sd, about 0.5% sd,or a range of values therebetween.

In some embodiments, a free-standing and/or self-supporting electrodefilm including a microparticulate non-fibrillizable binder describedherein may be characterized by a specific energy density 20-30% higherthan a wet battery electrode of comparable constitution, e.g., of activematerials.

In specific examples below, electrode films including a microparticulatenon-fibrillizable binder were fabricated.

Example 1

Dry battery anode electrode films were fabricated, which included 96% byweight graphite and 4% by weight binder, wherein the binder included 2%PTFE, 1% CMC and 1% PVDF. Other electrode film compositions can beenvisioned and prepared, and the disclosure herein is not limited to thespecific compositions disclosed.

Using a Hosokawa 100 AFG pressurized jet mill with a classifierattachment, as received CMC powders were milled with a size outputselection. Sigma Aldrich® sodium carboxymethylcellulose with a degree ofsubstitution of 1.2 was used as the feed material. A classifier rotationspeed of 8000 rpm was used in order to size select for a D₅₀ of 10 μm.Grind gas pressure was 120 psi with an initial chamber mass of 100 g.This resulted in a production rate of approximately 0.1 kg/hr. Picturesof the 100 AFG machine can be seen in FIGS. 2A and 2B. As received CMCpowder from Sigma Aldrich® had a D₅₀ particle size of approximately 70μm while the Hosokawa milled CMC had a D₅₀ of approximately 10 μm. Thisdifference can be seen in SEM images in FIGS. 3A and 3B. When Hosokawamilled CMC was used in a dry anode electrode parallel process, anincrease in first cycle efficiency and cell to cell consistency wasobserved compared to as received CMC. Electrochemical data for thiscomparison is shown in FIG. 4 . Using as received CMC, a charge anddischarge specific capacity of 386 mAh/g and 348 mAh/g respectively(90.2% efficiency) were achieved. Using milled CMC, a charge anddischarge specific capacity of 384 mAh/g and 349 mAh/g respectively(90.9% efficiency) were achieved.

In addition to electrochemical performance enhancement, the smaller D₅₀particle size of CMC mitigated electrode defects, such as holes, cracksor surface pits. Dry powder formulations using CMC powder as receivedfrom the manufacturer with D₅₀ particle size of 70 μm produced electrodefree-standing films with defects as observed in FIG. 5 . These defectswere circumvented using milled CMC with D₅₀ particle size of about 10 μmas illustrated in FIG. 6 . The rationale for these empirical resultslies in the larger surface area offered by the smaller D₅₀ CMC particlesize. At a fixed binder weight ratio in an electrode formulation, thehigher surface may offer a stronger binding strength to the activematerial powder matrix and a weaker affinity for the heated rollers usedto produce films or used to calender down film thicknesses. In contrast,the larger D₅₀ CMC particle size may offer a weaker binding strength tothe active materials powder matrix and a stronger affinity to heatedrollers used to produce films or used to calender down film thicknesses.This stronger affinity to the heated calender rollers can be attributedto a larger single spot size of the larger D₅₀ particle size of CMCbinder particles found in unmilled powder, which came into directcontact to the heated calender rollers during dry processing. As such,the larger CMC particles could be incidentally removed from theelectrode powder sample during powder-to-film formation or extractedfrom the film during film-to-film thickness reduction process, leavingbehind defects in the electrode. Tensile strength measurements offree-standing electrode films also support the idea that a strongerbinding cohesion strength of the finely milled CMC polymer binder. Thetensile strength results indicate that electrode films at similarthicknesses produced using CMC binder with a smaller D₅₀ particle size(10 μm vs. about 70 μm) were stronger than those produced with largerparticle size. Empirical results are presented in Table 1.

TABLE 1 Median Graphite Film Graphite Film CMC Type Particle SizeThickness Tensile Strength As received 73.4 ± 1.6 μm 300-301 μm 0.936 NResodyne processed 66.0 ± 2.3 μm 299-301 μm  1.01 N Jet milled 10.1 ±0.8 μm 298-300 μm  1.74 N (“Hosokawa”)

While certain embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms. Furthermore, various omissions, substitutions and changes in thesystems and methods described herein may be made without departing fromthe spirit of the disclosure. The accompanying claims and theirequivalents are intended to cover such forms or modifications as wouldfall within the scope and spirit of the disclosure. Accordingly, thescope of the present inventions is defined only by reference to theappended claims.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example described inthis section or elsewhere in this specification unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The protection is notrestricted to the details of any foregoing embodiments. The protectionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

Furthermore, certain features that are described in this disclosure inthe context of separate implementations can also be implemented incombination in a single implementation. Conversely, various featuresthat are described in the context of a single implementation can also beimplemented in multiple implementations separately or in any suitablesubcombination. Moreover, although features may be described above asacting in certain combinations, one or more features from a claimedcombination can, in some cases, be excised from the combination, and thecombination may be claimed as a subcombination or variation of asubcombination.

Moreover, while operations may be depicted in the drawings or describedin the specification in a particular order, such operations need not beperformed in the particular order shown or in sequential order, or thatall operations be performed, to achieve desirable results. Otheroperations that are not depicted or described can be incorporated in theexample methods and processes. For example, one or more additionaloperations can be performed before, after, simultaneously, or betweenany of the described operations. Further, the operations may berearranged or reordered in other implementations. Those skilled in theart will appreciate that in some embodiments, the actual steps taken inthe processes illustrated and/or disclosed may differ from those shownin the figures. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added. Furthermore, thefeatures and attributes of the specific embodiments disclosed above maybe combined in different ways to form additional embodiments, all ofwhich fall within the scope of the present disclosure. Also, theseparation of various system components in the implementations describedabove should not be understood as requiring such separation in allimplementations, and it should be understood that the describedcomponents and systems can generally be integrated together in a singleproduct or packaged into multiple products. For example, any of thecomponents for an energy storage system described herein can be providedseparately, or integrated together (e.g., packaged together, or attachedtogether) to form an energy storage system.

For purposes of this disclosure, certain aspects, advantages, and novelfeatures are described herein. Not necessarily all such advantages maybe achieved in accordance with any particular embodiment. Thus, forexample, those skilled in the art will recognize that the disclosure maybe embodied or carried out in a manner that achieves one advantage or agroup of advantages as taught herein without necessarily achieving otheradvantages as may be taught or suggested herein.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, and/or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, and/or steps are inany way required for one or more embodiments or that one or moreembodiments necessarily include logic for deciding, with or without userinput or prompting, whether these features, elements, and/or steps areincluded or are to be performed in any particular embodiment.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

What is claimed is:
 1. A method of fabricating a dry electrode film ofan energy storage device, comprising: mixing a dry microparticulatenon-fibrillizable binder with a first dry active material by a firstnondestructive mixing process to form a dry bulk active materialmixture; mixing a dry fibrillizable binder with a second dry activematerial by a high shear mixing process to form a dry structural bindermixture; mixing the dry bulk active material mixture and the drystructural binder mixture by a second nondestructive mixing process toform a dry electrode film mixture; and producing a free-standing dryelectrode film from the dry electrode film mixture.
 2. The method ofclaim 1, further comprising processing a dry non-fibrillizable binder athigh shear to form the dry microparticulate non-fibrillizable binder. 3.The method of claim 1, wherein the first and second nondestructivemixing processes are selected from the group consisting ofnondestructive jet milling, tumbling, paddle mixing, blade blending,acoustic mixing, and combinations thereof.
 4. The method of claim 1,wherein the high shear mixing process is selected from the groupconsisting of high shear jet milling, blending, and combinationsthereof.
 5. The method of claim 1, wherein producing the free-standingdry electrode film comprises processing the dry electrode film mixtureby a process selected from the group consisting of pressing,calendering, and combinations thereof.
 6. The method of claim 5, whereinthe producing the free-standing dry electrode film comprises heatedcalendering the dry electrode film mixture.
 7. The method of claim 1,wherein the method is a dry fabrication process.
 8. The method of claim1, wherein the dry microparticulate non-fibrillizable binder comprises aD₅₀ particle size of about 0.5-40 μm.
 9. The method of claim 1, whereinthe free-standing dry electrode film comprises a dry binder, wherein thedry binder comprises the dry fibrillizable binder and up to 50 wt. % ofthe microparticulate non-fibrillizable binder.
 10. The method of claim1, wherein the dry microparticulate non-fibrillizable binder is selectedfrom at least one of cellulose and a cellulose derivative.
 11. Themethod of claim 1, wherein the dry fibrillizable binder comprisespolytetrafluoroethylene (PTFE).
 12. The method of claim 1, wherein thefree-standing dry electrode film is substantially free of holes, cracksand surface pits.
 13. The method of claim 1, wherein the free-standingdry electrode film has a tensile strength of at least about 1 N.
 14. Themethod of claim 1, wherein at least one of the first and second dryactive materials comprise graphite.
 15. The method of claim 1, whereinthe free-standing dry electrode film comprises a thickness of at leastabout 250 μm.
 16. The method of claim 1, wherein the free-standing dryelectrode film further comprises an additional non-fibrillizable binder.17. The method of claim 16, wherein the additional non-fibrillizablebinder comprises polyvinylidene fluoride (PVDF).
 18. The method of claim1, wherein the dry electrode film comprises at least about 92 wt. % ofthe first and second dry active materials.
 19. The method of claim 1,further comprising contacting the free-standing dry electrode film ofclaim 1 with a current collector to form an electrode.
 20. The method ofclaim 19, further comprising inserting the electrode into a housing toform an energy storage device.
 21. The method of claim 20, wherein theenergy storage device is a battery.
 22. The method of claim 20, whereinthe energy storage device has a first cycle efficiency of at least about90%.